Maximum Likelihood Sequence Estimation (MLSE) is a mathematical algorithm to extract useful data out of a noisy data stream. An optimized detector for digital signals should do a best estimation of the transmitted data with the least possible number of errors, where the receiver emulates the distorted channel. All possible transmitted data streams are fed into this distorted channel model. The receiver compares the time response with the actual received signal and determines the most likely signal. In cases that are most computationally straightforward, root mean square deviation can be used as the decision criterion for the lowest error probability.
In Maximum Likelihood Sequence Estimation (MLSE), each sample of the received signal is associated with a sequence of symbols with respect to the (clock) phase of the sample within a received symbol. For example, a sample may be associated with a sequence of 5 decoded symbols, which may be the last 5 symbols that have been received, or the last 4 decoded symbols that have been received+the current decoded symbol.
The selection of which sample best represents the probability for each sequence of N consequent symbols has high impact on the achieved performance and hence called “match point selection”.
Mathematically, a match point D can be defined using the following equation for describing the probability metric used for MLSE decoder, defined by Eq. 1. The selection of D is the match point. In this case, the decision metrics is actually the estimated probability per symbol (Prob{ }).metric[symbol(i)]=(Prob{[symbol(i)|sample(i−D),decoded_symbols(i−D−1, . . . ,i−D−N)]}  [Eq. 1]where N is the number of consequent symbols that are assumed as ISA for decoding process and | denotes “given”.
However, while making a continuous estimation, a current optimal match point may change due to changes of channel frequency response, such as changes that may occur as a result of temperature changes. This means that there is a match point with better performance.
It is therefore an object of the present invention to provide a system and method for seamlessly changing the match point of an MLSE detector, detecting a sequence of symbols passing a communication channel, without disrupting the continuity of the output symbol stream.
It is another object of the present invention to provide a system and method for seamlessly changing the match point of an MLSE detector, detecting a sequence of symbols passing a communication channel, without adding errors to the decoded symbols.
Other objects and advantages of the invention will become apparent as the description proceeds.